IFS including control arm and strut supported by steering knuckle load arm

ABSTRACT

An IFS assembly having a single lower control arm having an inboard end pivotally secured to a chassis support structure, an air spring supported by an air spring seat relative to the lower control arm, a strut having an upper end pivotally secured to the chassis support structure and a lower end coupled to the lower control arm outboard end, and a steering knuckle fixed to the strut lower end, the steering knuckle disposed below the lower air spring seat and whose rotative movement about the strut axis is unconfined by proximity between the steering knuckle and the tower air spring seat, whereby available wheel cut is maximized. Also an IFS module including right and left side IFS assemblies and adapted for installation into a vehicle.

BACKGROUND

The present disclosure relates to vehicle suspension systems,particularly independent front suspension (“IFS”) assemblies.

IFS assemblies employing struts, which are capable of supporting a sideload and typically provide damping capabilities, are well known. It isalso known to provide an IFS assembly including struts that provideupward support axially therealong, and such suspensions typically employa single lower control arm. Moreover, it is known to employ air springswith such struts. For example, MacPherson type strut IFS assemblieswherein an air spring is located above and generally in line with thestrut are disclosed by U.S. Pat. Nos. 4,206,907; 4,655,438; 4,974,872;and 6,382,602. Of these patents, the '907 and '602 patents also disclosevarying the air spring pressure for load and ride height adjustmentpurposes.

Further examples of MacPherson type strut IFS assemblies in which coilsprings and leaf springs are located between a single tower control armand the vehicle chassis are disclosed by U.S. Pat. Nos. 2,018,653;2,842,230; 2,967,066; 3,333,653; 3,926,454; and 4,653,772.

It is also known to provide MacPherson type strut IFS assemblies whereinthe steering knuckle includes an arm portion extending below andtransferring the load to the strut, as disclose, for example, in U.S.Pat. No. 5,192,100.

It is desirable to reduce loading of both struts and air springs in anIFS assembly, to maximize the available wheel cut of an IFS assembly, tosimplify vehicle suspension installations by OEM manufacturers, providevariable load-carrying and right height capabilities, and provide otheradvancements in areas of IFS technologies and configurations.

SUMMARY

The present disclosure beneficially provides such advancements.

According to a first aspect, the present disclosure provides an IFSassembly including a single lower control arm having laterally-spacedinboard and outboard ends, the inboard end adapted to be pivotallysecured to a chassis support structure. A lower air spring seat issupported by the lower control arm, the lower air spring seat adapted toupwardly support the chassis support structure relative to the lowercontrol arm through an air spring engaging the chassis supportstructure. The IFS assembly includes a strut having upper and lower endsdisposed along a strut axis, the strut upper and lower ends havingrelative movement along and about the strut axis. The strut upper end isadapted to be pivotally secured to the chassis support structure and thestrut lower end is coupled to the lower control arm outboard end. Asteering knuckle is rotatably and axially secured to the strut lowerend, the steering knuckle disposed below the lower air spring seat andhas rotative movement about the strut axis that is unconfined byproximity between the steering knuckle and the lower air spring seatand/or the air spring through which the lower air spring seat is adaptedto support the chassis support structure. Consequently, available wheelcut is maximized.

According to a second aspect, the present disclosure provides an IFSassembly including a chassis support structure and a single lowercontrol arm having laterally-spaced inboard and outboard ends, theinboard end pivotally secured to the chassis support structure. A lowerair spring seat is supported by the lower control arm, and an air springis supported by the lower air spring seat and engages the chassissupport structure. The chassis support structure is upwardly supportedby the air spring relative to the lower air spring seat. The IFSassembly includes a strut having upper and lower ends disposed along astrut axis, the strut upper and lower ends having relative movementalong and about the strut axis. The strut upper end is pivotally securedto the chassis support structure, and the strut lower end is coupled tothe lower control arm outboard end. A steering knuckle is rotatably andaxially secured to the strut lower end and is disposed below the lowerair spring seat. The steering knuckle has rotative movement about thestrut axis that is unconfined by proximity between the steering knuckleand the lower air spring seat. Consequently, available wheel cut ismaximized.

According to a third aspect, the present disclosure provides an IFSassembly including a single lower control arm defining laterally-spacedinboard and outboard ends, the inboard end adapted to be pivotallysecured to a chassis support structure. The IFS assembly includes astrut having upper and lower ends disposed along a strut axis, the strutupper and lower ends having relative movement along and about the strutaxis. The strut upper end is adapted to be pivotally secured to thechassis support structure. The IFS assembly includes a steering knuckleincluding a strut supporting portion affixed to and supporting the strutlower end, and a load arm extending below and secured to the lowercontrol arm. The outboard end of the lower control arm is disposedbetween the load arm and the strut lower end, and the lower control armis upwardly supported by the load arm.

According to a fourth aspect, the present disclosure provides an IFSassembly including a chassis support structure and a single lowercontrol arm defining laterally-spaced inboard and outboard ends, theinboard end pivotally secured to the chassis support structure. The IFSassembly includes a strut having upper and lower ends disposed along astrut axis, the strut upper and lower ends having relative movementalong and about the strut axis. The strut upper end is pivotally securedto the chassis support structure. The IFS assembly includes a steeringknuckle including a strut supporting portion affixed to and supportingthe strut lower end, and a load arm extending below and secured to thelower control arm. The outboard end of the lower control arm is disposedbetween the load arm and the strut lower end, and the lower control armis upwardly supported by the load arm.

According to a fifth aspect, the present disclosure provides an IFSassembly including a single lower control arm defining laterally-spacedinboard and outboard ends, the inboard end adapted to be pivotallysecured to a chassis support structure, and a steering knuckle securedto the lower control arm outboard end. The IFS assembly includes a struthaving upper and lower ends disposed along a strut axis, the strut upperand lower ends having relative movement along and about the strut axis.The strut lower end is fixed relative to the steering knuckle, and thestrut upper end provided with a clevis ring structure adapted tosurround a bushing extending therethrough. The strut upper end isadapted to be pivotally secured to the chassis support structure throughthe clevis ring structure and the bushing about a generally horizontalfirst axis.

According to a sixth aspect, the present disclosure provides an IFSassembly including a chassis support structure and a single lowercontrol arm defining laterally-spaced inboard and outboard ends, theinboard end pivotally secured to the chassis support structure. Asteering knuckle is secured to the lower control arm outboard end. TheIFS assembly includes a bushing and a strut having upper and lower endsdisposed along a strut axis, the strut upper and lower ends havingrelative movement along and about the strut axis. The strut lower end isfixed relative to the steering knuckle, and the strut upper end providedwith a clevis ring structure. The bushing extends through and issurrounded by the clevis ring structure, and the strut upper end ispivotally secured to the chassis support structure through the clevisring structure and the bushing about a generally horizontal first axis.

According to a seventh aspect, the present disclosure provides an IFSassembly including a single lower control arm having laterally-spacedinboard and outboard ends, the inboard end adapted to be pivotallysecured to a chassis support structure, and a steering knuckle securedto the lower control arm outboard end. The IFS assembly includes a struthaving upper and lower ends disposed along a strut axis, the strut upperand lower ends having relative movement along and about the strut axis.The strut lower end is fixed relative to the steering knuckle. A torquetube assembly includes an elongate torque tube extending between firstand second joints at which the torque tube is adapted to be rigidlyfixed relative to the chassis support structure, and an upper strutmount having laterally-spaced first and second ends. The first end isrigidly affixed to the torque tube between the first and second joints.The strut upper end is adapted to be pivotally secured to the secondend.

According to an eighth aspect, the present disclosure provides an IFSassembly including a chassis support structure having a first portionand a torque tube assembly, and a single lower control arm havinglaterally-spaced inboard and outboard ends. The inboard end is pivotallysecured to the chassis support structure first portion, and a steeringknuckle is secured to the lower control arm outboard end. The IFSassembly includes a strut having upper and lower ends disposed along astrut axis, the strut upper and lower ends having relative movementalong and about the strut axis. The strut lower end is fixed relative tothe steering knuckle. The torque tube assembly includes an elongatetorque tube extending between first and second joints at which thetorque tube is rigidly fixed relative to the chassis support structurefirst portion, and an upper strut mount having laterally-spaced firstand second ends. The first end is rigidly affixed to the torque tubebetween the first and second joints, and the strut upper end ispivotally secured to the second end.

According to a ninth aspect, the present disclosure provides an IFSmodule adapted for installation into a vehicle. The IFS module includesa chassis support structure having laterally opposite right and leftsides, and adapted for attachment to the vehicle frame. The IFS moduleincludes a pair of left and right side single lower control arms, eachlower control arm defining laterally-spaced inboard and outboard ends,and each inboard end is pivotally secured to the chassis supportstructure. The IFS module includes a pair of left and right side struts,each strut having upper and lower ends disposed along a respective strutaxis, the upper and lower ends of each strut having relative movementalong and about the respective strut axis. The strut upper ends arepivotally secured to the chassis support structure. The IFS module alsoincludes a pair of left and right side steering knuckles, each steeringknuckle fixed relative to the respective strut lower end and secured tothe respective lower control arm outboard end.

BRIEF DESCRIPTION OF THE DRAWINGS

The various objects, features and attendant advantages of the presentinvention will become fully appreciated as the same becomes betterunderstood when considered in conjunction with the accompanyingdrawings, wherein like reference characters designate the same, similaror corresponding parts throughout the several views:

FIG. 1 is a rear, upper perspective view of an IFS module incorporatingright and left side IFS assemblies according to an embodiment of thepresent disclosure;

FIG. 2 is a top plan view of the IFS module of FIG. 1;

FIG. 3 is a rear elevation of the IFS module of FIG. 1;

FIG. 4 is a bottom plan view of the IFS module of FIG. 1;

FIG. 5 is right side elevation of the IFS module of FIG. 1;

FIG. 6 is a partially sectioned view of the IFS module of FIG. 5 alongline 6-6;

FIG. 7 is a partially exploded, front, upper perspective view of the IFSmodule of FIG. 1;

FIG. 8 is a front, upper perspective view of the IFS module of FIG. 1;

FIG. 9 is a longitudinal sectional view of a first embodiment strut usedin an IFS assembly according to the present disclosure; and

FIG. 10 is a longitudinal sectional view of a second embodiment strutused in an IFS assembly according to the present disclosure.

DETAILED DESCRIPTION

The invention is adaptable to various modifications and alternativeforms, and the specific embodiments thereof shown by way of example inthe drawings are herein described in detail. The exemplary embodimentsof the present disclosure are chosen and described so that othersskilled in the art may appreciate and understand the principles andpractices of the present disclosure. It should be understood, however,that the drawings and detailed description are not intended to limit theinvention to the particular forms disclosed, but on the contrary, theintention is to cover all modifications, equivalents and alternativesfalling within the spirit and scope of the present invention as definedby the appended claims.

FIGS. 1-8 depict an embodiment of IFS module 20 which is a free standingassemblage adapted for installation into a vehicle. IFS module 20 may beaffixed to vehicle frame 22 shown in dashed lines in FIG. 1, forexample. IFS module 20 includes chassis support structure 24 havingright side 26 and left side 28 sharing substantially rigid chassissupport structure first portion 29 to which is attached, or which formsa part of, right side IFS assembly 30 and left side IFS assembly 32.Alternatively, chassis support structure 24 or first portion 29 thereofmay form an integral part of the vehicle to which right and left sideIFS assemblies 30, 32 are installed directly, rather than through an IFSmodule such as IFS module 20. Chassis support structure 24 may be astamped sheet metal and/or metal beam weldment formed of suitably rigidmaterial. Chassis support structure right and left sides 26, 28 as shownare substantially mirror images of each other. In other words, chassissupport structure 24 is substantially symmetrical about its lateralcenter, which coincides with the lateral center of the vehicle.Likewise, right and left side IFS assemblies 30, 32 as shown aresubstantially mirror images of each other. Unless indicated otherwise,structural and functional descriptions herein which specify neitherchassis support structure right or left side 26, 28, nor right or leftside IFS assembly 30, 32, or components thereof, should be construed torelate to the chassis support structure, IFS assembly and components ofeither side. Moreover, corresponding elements between the right and leftsides have a common reference numeral and in the accompanying Figures,the element of only the right or left side element may be indicated.

In the depicted embodiment, each IFS assembly 30, 32 includes lowercontrol arm 34, strut 36 which extends generally vertically along itsstrut axis 37, steering knuckle 38, and torque tube assembly 40. Asshown, torque tube assembly 40 is an integrated part of the respectivechassis support structure right or left side 26, 28, but may be aseparate component affixed thereto. Torque tube assembly 40 is formed ofan elongate torque tube 42 that extends fore and aft along generallyhorizontal axis 43, and laterally extending upper strut mount 44.Relative to chassis support structure first portion 29, torque tube 42is secured at fixed forward joint 63 and aft joint 64 spaced alongtorque tube axis 43. Joints 63, 64 may be welds. Upper strut mount 44has inboard end 45 affixed, as by welds, to torque tube 42 at a locationbetween joints 63, 64, and outboard end 46 which extends laterallyoutward from inboard end 45 in a generally horizontal plane.

Strut upper end 48 and strut lower end 50 are disposed along strut axis37, and have relative movement along and about strut axis 37. Strutupper end 48 is provided with steel clevis ring structure 52 thatsurrounds hushing 54. In the depicted embodiment, bushing 54 is acompliance bushing formed of elastomeric material such as vulcanizedrubber surrounding and bonded to cylindrical steel sleeve 55 and/or theinterior surface of clevis ring structure 52. Sleeve 55 is concentricwith clevis ring structure 52, and compliance bushing 54 may be acomponent part of strut 36. Strut upper end 48 is pivotally secured toupper strut mount outboard end 46 with bolt 56 and nut 57. Bolt 56extends along axis 58 through upper strut mount outboard end 46 andbushing sleeve 55. In the depicted embodiment, upper strut mount 44 isdefined by an inverted U-shaped channel having spaced parallel forwardflange 60 and aft flange 62 provided at outboard end 46 with aperturesaligned along axis 58. Upper strut mount 44, strut upper end 48, andelongate bolt 56 thus define a clevis joint. The interior of bushingsleeve 55 is closely fitted about bolt 56 to resist rotation of strutupper end 48 with strut lower end 50, though a degree of compliance isobtained through elastic deformation of compliance bushing 54, generallyin a plane perpendicular to strut axis 37. Strut upper end 48 also has anominal position relative to chassis support structure 24 in which theaxes of bolt 56, bushing sleeve 55 and clevis ring structure 52 arecoincident with axis 58, and strut axis 37 is substantiallyperpendicular to axis 58. In the nominal position, elasticallydeformable compliance bushing 54 is substantially undeformed. Deviationfrom the nominal position is the result of the compliance facilitated byelastic deformation of bushing 54. Deviation from the nominal positionis typically caused by angular displacement of clevis ring structure 52about strut axis 37 due to frictionally induced torque imparted on strutupper end 48 by strut lower end 50, at the onset of or during rotativemovement of steering knuckle 38 about strut axis 37. In someembodiments, deviation from the nominal position may also be caused bystrut 36 experiencing a bending moment in fore or aft directionsgenerally parallel with axis 58.

Strut lower end 50 is fixed at two locations along strut axis 37 tostrut supporting portion 66 of steering knuckle 38. Strut supportingportion 66 includes encircling clamp 65 which surrounds strut lower end50 received therethrough, and boss 67 and mating bracket 68 locatedbelow encircling clamp 65. Each of boss 67 and bracket 68 is configuredwith a semi-cylindrical inner surface that engages the outer cylindricalsurface of strut lower end 50. The semi-cylindrical inner surfaces ofboss 67 and bracket 68 are provided with circumferentially extending,radially inwardly projecting ridges 70 that are received in cooperatingcircumferential groove 71 (FIGS. 9 and 10) provided in the cylindricalouter surface of strut lower end 50. Ridges 70 and groove 71 axiallyalign strut lower end 50 relative to steering knuckle 38 and secure themagainst relative movement along strut axis 37. Frictional engagementbetween the cylindrical outer surface of strut lower end 50 and theinterfacing cylindrical surfaces of encircling clamp 65, and the clampdefined by boss 67 and bracket 68, rotatably and axially fix strut lowerend 50 to steering knuckle strut supporting portion 66. Bolts 72 holdbracket 68 and boss 67 together against strut lower end 50; bolt 72 andnut 73 hold encircling clamp 65 tightly closed upon strut lower end 50.

Certain embodiments of IFS module 20 are provided with components thatmay be included in IFS assembly 30, 32 as individually installed in avehicle, or which may be installed subsequent to installation of the IFSassemblies 30, 32. Steering knuckle 38 includes caliper assembly mounts74 and spindle 76, to which caliper assembly 78 and rotor 80 of diskbrake assembly 82 are respectively attached. Rotor 80 as shown isprovided with central wheel mounting flange 81 provided with wheelmounting lugs 83 for attachment of the vehicle wheels (not shown). Aportion of rotor 80 is disposed within caliper assembly 78 in a mannerwell-known to those having ordinary skill in the art, whereby caliperassembly 78 and rotor 80 are operatively engageable. As discussed hereinbelow, IFS assembly 30, 32 maximizes the available wheel cut, i.e., theangle in either direction about strut axis 37 that a vehicle front wheelcan be turned.

As perhaps best seen in FIGS. 4 and 6, steering knuckle 38 is providedwith load arm 84 that extends laterally inwardly and below lower controlarm 34, to which load arm is secured. Steering knuckle 38 also haselongate turning arm 86 which, in the depicted embodiment, extendsrearwardly and laterally inwardly from load arm 84 to turning armterminal end 88. Lower control arm 34 has laterally-spaced inboard andoutboard ends 90, 92. Lower control arm inboard end 90 is pivotallysecured to chassis support structure first portion 29 at a pair oflocations that are spaced fore and aft. These pivotal attachments areabout generally horizontal and parallel forward and aft axes 94, 96 thatextend fore and aft, the attachments being made with bolts 98 and nuts100, as perhaps best seen in FIG. 4.

Lower control arm outboard end 92 is rotatably secured to, and isupwardly supported by, steering knuckle toad arm 84 throughinterconnecting ball joint 102. Steering knuckle 38 thus places acompressive force onto ball joint 102 and lower control arm 34. Strutaxis 97 extends through ball joint 102. Referring to FIGS. 6 and 7,lower control arm outboard end 92 has top surface 104 disposed aboveball joint 102 and is superposed by strut axial end 106 defined by strutlower end 50. As noted above, strut lower end 50 is axially supported bysteering knuckle strut supporting portion 66, and so strut axial end 106is in spaced superposition with top surface 104. Thus, lower control armoutboard end 92 is sandwiched between strut 36 and steering knuckle loadarm 84 along strut axis 37.

IFS module 20 includes steering box 108 having housing 109 secured tochassis support structure first portion 29 at a laterally centralposition between right and left side lower control arm inboard ends 90.Steering box 108 has rotatable input shaft 110 extending rearwardly fromhousing 109, the rearward end of input shaft 110 adapted to be rotatablyconnected to a steering shaft (not shown). Steering box 108 also hasrotatable output shaft 112 downwardly extending through an aperture inchassis support structure first portion 29 at the lateral center ofchassis support structure 24. Rotatable input and output shafts 110, 112are operably coupled within housing 109 for corresponding rotation.Pitman arm 114 is rotatably secured to steering box output shaft 112 andconverts angular movement of output shaft 112 to linear movement of apair of elongate right and left side tie rods 116 each individuallysecured at one end to pitman arm 114 via an interconnecting tie rod end118, as perhaps best seen in FIG. 4. Each tie rod 116 is secured at itsopposite end to a turning arm terminal end 88 via an interconnecting tierod end 118. Pitman arm 114, tie rods 116 and tie rod ends 118 thus formsteering linkage between steering box 108 and turning arms 86, throughwhich coordinated rotative movements of right and left side steeringknuckles 38 about their respective strut axes 37 is accomplished, theserotative movements induced by rotation steering box input shaft 110through steering box output shaft 112 and the steering linkage.

IFS module 20 and the IFS assemblies 30, 32 include a pair of right andleft side air springs 120 operably disposed between the respectivechassis support structure right or left side 26, 28 and the respectiveright or left side lower control arm 34. Each air spring 120 engageschassis support structure 24 at a respective right or left side location122 at which the air spring is retained to chassis support structure 24with threaded fastener 124. Chassis support structure 24 and air springs120 are upwardly supported relative to lower control arms 34, and thusby steering knuckle load arms 84.

Air spring 120 is supported by lower air spring seat 126, which issupported by seat support structure 128 of lower control arm 34. Seatsupport structure 128 is located laterally between tower control arminboard and outboard ends 90, 92, and projects upwardly relativethereto. Seat support structure 128 includes rigid strut member 130which extends along longitudinal axis 132 between lower air spring seat126 and a location on lower control arm 34 proximate its outboard end92, as perhaps best seen in FIGS. 1 and 3. Steering knuckle 38 isdisposed below lower air spring seat 126 and air spring 120, and rigidstrut member longitudinal axis 132 diverges from strut axis 37 in anupward direction from lower control arm 34. Lower air spring seat 126,air spring 120, and rigid strut member 130 are thus located well out ofthe path of rotative movement of steering knuckle 38 and disk brakeassembly 82 carried thereby, whereby rotative movement of steeringknuckle 38 about strut axis 37 is unconfined by proximity betweensteering knuckle 38 and lower air spring seat 126 and/or air spring 120is unconfined by proximity therebetween and available wheel cut ismaximized. Moreover, a portion of disk brake assembly 82 carried bysteering knuckle 38 is receivable beneath lower air spring seat 126during rotative movement of steering knuckle 38 about strut axis 37.

FIG. 9 shows the internal structure and further details of strut 36, andFIG. 10 shows the internal structure and details of alternativeembodiment strut 36 a, which may be substituted for strut 36. Except fordistinctions between strut 36 and strut 36 a discussed below andrevealed by a comparison between FIGS. 9 and 10, reference herein and inFIGS. 1-8 to strut 36 shall be understood to apply to and encompassstrut 36 a. Additionally, it is to be understood that the horizontalorientation of struts 36, 36 a depicted in FIGS. 9 and 10 is merely toprovide a larger view than obtainable by depicting them in asubstantially vertical orientation, and does not alter the context usedheretofore with respect to descriptors such as “upper” and “lower”;“above” and “below”; “top” and “bottom”; “vertical” and “horizontal”;and the like.

Referring to FIG. 9, strut upper end 48 is defined by cylindrical strutupper portion 134 and strut lower end 50 is defined by cylindrical strutlower portion 136. Strut upper and lower portions 134, 136 aretelescopically engaged along strut axis 37, and respectively form astrut rod and a strut body. Strut lower portion 136 is sealably closedat its free end by end cap 138 that defines above-mentioned strut axialend 106. Above-mentioned clevis ring structure 52 is sealably fixed tothe free end of strut upper portion 134. Concentrically disposed withinstrut upper portion 134 is cylindrical damper body 140, within which isslidably disposed annular damper valve 142. Damper valve 142 is affixedto one end of elongate damper rod 144 that extends therethrough. Theopposite end of damper rod 144 is secured to plate 145 sealably fixed tothe interior wall of strut lower portion 136 and relative to end cap138. One end of cylindrical damper body 140 is sealably affixed to strutupper end 48; the opposite end of damper body 140 is affixed to slidingbearing member 146. The cylindrical space between the superposingcylindrical surfaces of strut upper portion 134 and strut lower portion136 located above sliding bearing member 146 is vented to atmosphere.Sliding bearing member 146 is slidably disposed within cylindrical lowerportion 136, and surrounds and moves axially along valve rod 144.Sealably surrounding valve rod 144 at the end of damper body 140 affixedto sliding bearing member 146, and located below the lower side ofdamper valve 142 is annular seal 147. Above the upper side of dampervalve 142 is disk-shaped floating piston 148, slidably sealed to theinner diameter of damper body 140. First oil chamber 150 is definedbetween damper valve 142 and floating piston 148, and second oil chamber152 is defined between damper valve 142 and annular seal 147, therebydefining internal monotube damper assembly 1153 having controlled oilflow across damper valve 142 between first and second oil chambers 150,152 along the path defined by arrow 154. Damper 153 is thus housedwithin strut upper and lower portions 134, 136 and dampens relativemotion between strut upper and lower ends 48, 50 along strut axis 37.

Also housed within strut upper and lower portions 134, 146 is gas spring156, which may utilize high pressure nitrogen as the working fluid. Gasspring 156 includes first gas chamber 158 located in damper body 140between clevis ring structure 52 and floating piston 148, and second gaschamber 160 located in strut lower portion 136 and sliding bearingmember 146 annular seal 147 and plate 145. The pressurized nitrogen gaswithin gas spring 156 provides the biasing force that urges strut upperand lower ends 48, 50 apart along strut axis 37, and thus allows struts39 to upwardly support chassis support structure 24 relative to steeringknuckles 38. Additionally, the high pressure nitrogen gas within gasspring, which acts on the upper side of floating piston 148, preventscavitation in the hydraulic oil of damper 153. First gas chamber 158 isprovided with a circumferentially arranged plurality of orifices 162through the cylindrical wall of damper body 140 proximate the axial endthereof. First and second gas chambers are in fluid communication alonga path indicated by arrow 164, which extends through orifices 162, alongthe outer cylindrical surface of damper body 140, and about damper rod144 within sliding bearing member 146. Above the axial end ofcylindrical damper body 140, in clevis ring structure 52, strut upperend 48 is provided with gas port 166 adapted for connection with gasreservoir 168 externally of strut 36. IFS module 20 includes right andleft side gas reservoirs 168 respectively mounted to chassis supportstructure right and left sides 26, 28. Each gas spring 156 is adapted toreceive gas from and discharge gas to its connected gas reservoir 168,and is capable of containing gas at selectively variable pressures so asto compensate for different loads between the strut upper and lower ends48, 50 and/or establish different nominal axial distances therebetween,thereby enabling changes to vehicle ride height and providing vehiclekneeling capabilities.

Referring now to FIG. 10, strut 36 a is substantially identical to strut36 except for providing circular wall 170 sealably fixed withincylindrical damper body 140 just below orifices 162, and sealed, thirdgas chamber 172 within damper body 140 between wall 170 and floatingpiston 148. Third gas chamber 172 provides damper 153 with a sealednitrogen charge which bears on the upper side of floating piston 148.

Forces imparted by the pressurized nitrogen in gas spring 156 urge strutupper and lower ends 48, 50 apart, and struts 36, 36 a thereforeupwardly support chassis support structure 24. Struts 36, 36 a act inparallel with air springs 120 to upwardly support chassis supportstructure 24 and other portions of a vehicle's sprung weight relative todifferent portions of steering knuckles 38. Air springs 120 may thus besmaller than prior air springs operably disposed in series connectionwith struts or other springs, and positioned so as not to constrainrotative movement of the steering knuckles, maximizing available wheelcut.

While exemplary embodiments have been disclosed hereinabove, the presentinvention is not limited thereto. Instead, this application is intendedto cover any variations, uses, or adaptations of the present disclosureusing its general principles.

What is claimed is:
 1. An IFS assembly comprising: a single lowercontrol arm defining laterally-spaced inboard and outboard ends, theinboard end adapted to be pivotally secured to a chassis supportstructure; a strut having upper and lower ends disposed along a strutaxis, the strut upper and lower ends having relative movement along andabout the strut axis, the strut upper end adapted to be pivotallysecured to the chassis support structure; a steering knuckle comprisinga strut supporting portion affixed to and supporting the strut lowerend, and a load arm extending below and secured to the lower controlarm, the outboard end of the lower control arm sandwich between the loadarm and the strut lower end, the lower control arm upwardly supported bythe load arm; a lower air spring seat supported by the lower controlarm, the lower air spring seat adapted to upwardly support the chassissupport structure relative to the lower control arm through an airspring engaging the chassis support structure; wherein the lower controlarm includes a seat support structure located laterally between thelower control arm inboard and outboard ends and supporting the lower airspring seat, the seat support structure projecting upwardly relative tothe lower control arm inboard and outboard ends; and wherein the seatsupport structure includes a rigid strut member extending between thelower air spring seat and a location on the lower control arm proximatethe lower control arm outboard end.
 2. The IFS assembly of claim 1,wherein the rigid strut member has a longitudinal axis that divergesfrom the strut axis in an upward direction from the lower control arm.3. An IFS assembly comprising: a chassis support structure; a singlelower control arm defining laterally-spaced inboard and outboard ends,the inboard end pivotally secured to the chassis support structure; astrut having upper and lower ends disposed along a strut axis, the upperand lower end having relative movement along and about the strut axis,the strut upper end pivotally secured to the chassis support structure;a steering knuckle comprising a strut supporting portion affixed to andsupporting the strut lower end, and a load arm extending below andsecured to the lower control arm, the outboard end of the lower controlarm sandwiched between the load arm and the strut lower end, the lowercontrol arm upwardly supported by the load arm; an air spring engagingthe chassis support structure and a lower air spring seat disposedbeneath the air spring and supported by the lower control arm, thechassis support structure upwardly supported relative to the lowercontrol arm through the air spring and lower air spring seat; whereinthe lower control arm includes a seat structure located laterallybetween the lower control arm inboard and outboard ends and supportingthe lower air spring seat, the seat support structure projectingupwardly relative to the lower control arm inboard and outboard ends;and, wherein the seat support structure includes a rigid strut memberextending between the lower air spring seat and a location on the lowercontrol arm proximate the lower control arm outboard end.
 4. The IFSassembly of claim 3, wherein the rigid strut member has a longitudinalaxis that diverges from the strut axis in an upward direction from thelower control arm.